8 papers · 1 filter
Infrared Number Counts of AGN in the GOODS Fields
E. Treister, C. Megan Urry, the GOODS AGN Team
Using the known numbers and evolution of unobscured AGN, and assuming that there is a large number of corresponding obscured AGN -- as expected if AGN unification is correct -- we…
Type II quasar candidates in the Sloan Digital Sky Survey: evidence for X-ray obscuration
C. Vignali, D. M. Alexander, A. Comastri
Recent X-ray surveys with Chandra and XMM-Newton have found several genuine Type II quasars, the long sought-after population of high-luminosity (high-redshift) Seyfert 2 galaxies,…
Spectropolarimetry of Compton-thin Seyfert 2s
S. L. Lumsden, D. M. Alexander, J. H. Hough
We present new spectropolarimetry of a sample of nearby Compton-thin Seyfert 2 galaxies (ie those with N_H<10^23 cm^-2). We show that the detection rate of scattered broad Halpha i…
X-rays from the First Massive Black Holes
W. N. Brandt, C. Vignali, D. P. Schneider +7
X-ray studies of high-redshift (z > 4) active galaxies have advanced substantially over the past few years, largely due to results from the new generation of X-ray observatories. A…
On the nature of Extremely Red Objects: the 2 Ms Chandra Deep Field-North Survey results
C. Vignali, D. M. Alexander, F. E. Bauer +4
Understanding the nature of Extremely Red Objects [EROs; (I-K)>=4] is one of the most challenging issues in observational cosmology. Here we report on the X-ray constraints provide…
Exotic sources detected in the 1 Ms Chandra Deep Field North Survey
D. M. Alexander, F. E. Bauer, W. N. Brandt +4
We provide constraints on optically faint (I>=24) X-ray sources, z>6 AGN, Very Red Objects (VROs; I-K>=4), and optically faint radio sources using the 1 Ms Chandra Deep Field North…